A tax on medical marijuana could generate some $400,000 for Washington, D.C., over the next five years, according to an estimate from the city’s top financial official.

Washington’s Office of the Chief Financial Officer provided the estimate to the D.C. Council, which has proposed taxing marijuana as part of budget negotiations.

The council passed legislation earlier this year that permits residents with certain medical conditions such as HIV, AIDS, glaucoma, cancer and multiple sclerosis to purchase marijuana to help with their illnesses.

The budget council members are expected to vote June 15 on a provision that would impose the city’s 6 percent sales tax on medical marijuana sold in the city.